This invention relates to the movement of vials or containers from one location to another by a transport mechanism. More particularly, the invention relates to the movement of liquid sample-containing vials in a chemical analysis system from a tray to one or more sample preparation and/or analysis stations.
Automation of chemical analyses which were once performed by hand has progressed significantly. In the field of liquid chromatography, a number of automated chromatographic analysis systems are currently commercially available. These systems, referred to as autosamplers, aid in the automation of chromatographic analysis by storing a number of individual samples and injecting them sequentially into a chromatograph for analysis. The chromatographic analysis, which typically takes between about 10 to 60 minutes, can be completed without human intervention.
Some early autosampler systems used circular trays having a single row of sample-containing vials about the periphery thereof. Typically, the vials are of a small (i.e., 1.8 ml) volume and fabricated of glass. The vials may be sealed with a rubber septum held onto the top of the vial by a cap with a hole in the center thereof. The hole exposes a portion of the rubber septum to a hollow needle which is pushed through the septum and into the sample.
The needle is used to withdraw a predetermined amount of the sample and then cause that sample to be injected into the chromatograph. In these early autosamplers, the tray holding the vials rotated to position succeeding vials beneath the needle. The needle was then lowered, sample removed, and the withdrawn. The withdrawn sample was then injected into the sample loop of an injection valve.
Autosampler systems of more recent vintage still perform the same basic tasks. However, demand has increased for systems which are capable of storing an increased number of sample vials in less space. The quality of chromatography columns has improved so that analysis time for an individual sample has decreased to 10 minutes or less. End users of the autosamplers desire a system which can be loaded with enough samples to run several hours, and preferably overnight, without further human intervention.
This has led to the development of several different tray configurations including smaller circular trays arranged on a planetary platter. Bradley et al, U.S. Pat. No. 4,622,457, shows this tray configuration. Other autosamplers use trays containing multiple rows of vials in a rectangular configuration. Most of these systems, however, still place the sample-containing vials in a stationary matrix and move a needle to the vial to be sampled. Thus, the typical autosampler includes three motors for movement of the needle in the X and Y directions, as well as the Z direction, for sample withdrawal.
Currently, additional demands are being placed on such autosampler systems to increase further the automation of the chemical analyses. In addition to automated sampling, there is the desire to produce systems capable of some sample preparation. For example, there may be a need to dilute the sample before analysis or to add a reagent to aid in sample detection. Some reagents may take several minutes to react and may require continuous mixing and/or heating at elevated temperatures. As this time is comparable to the time required for chromatographic analysis, it may be desirable to have more than one sample in process at one time.
Further, it may become necessary to remove a sample from the tray matrix and perform an operation on it such as mixing or heating. As it is difficult to control a system where more than one device moves over a stationary matrix of vials to perform simultaneous operations, and since some operations may be better performed by removal from the matrix, a system which has the capability to remove vials from a matrix and transport them to work stations where these sample-preparation operations may be performed has significant advantages over systems which are incapable of this function.
Commercial systems have been developed for sample preparation which have the capability of moving sample vials from location to location. Such systems use robotic arms to grasp the vials and move them. However, the need for a gripping capability requires the addition of yet another motor which actuates the gripping mechanism in the system. This adds to the cost and complexity of such systems. Accordingly, there is a need in the art for an autosampler which is capable of removing sample-containing vials from a matrix and transporting the vials from one location to another within the system, but which is simpler to operate and less expensive to manufacture than previous systems.